The Naples club moved a point closer to securing a UEFA Champions League at San Siro on Saturday, but there were concerns when Argentina striker Higuain was carried off following a challenge with Inter defender Marco Andreoll late in the Serie A game.
After spurning a couple of opportunities to add to his 17-goal tally in the league, the former Real Madrid man contested a 50-50 challenge with Andreolli and came off worse.
The sight of the 26-year-old in considerable pain will also be a concern for Argentina coach Alejandro Sabella ahead of the upcoming FIFA World Cup.
And with Napoli's next fixture comes in the Coppa Italia final against Fiorentina on Friday, Benitez faces an anxious wait to discover how badly injured the 26-year-old is.
"Higuain has a trauma to the ankle, a bruise and we'll have to see over the next few days," he told Sky Italia.
"We still don’t know what the situation is."
Benitez was left to rue his side's inability to secure all three points after they had the better of the game, which was his first back at his former employers since he was sacked by Inter in 2010.
"I think the team played to win," he added. "We had a lot of possession against a very strong side that has played only one game per week since the start of the season.
"We pushed hard and I think against them it was a good result, though we could also have won tonight.
"I always seek balance. If the team concedes, then we have to score more goals. I saw the team do well at both ends of the field tonight, but we couldn't get the goal."
